1. Field of the Invention
This invention relates generally to a process for controlling, and thus predicting, the microstructural bias of multi-phase composites. This invention relates specifically to a process for obtaining preferential positioning of the component phases present in the microstructure of multi-phase particulate composite materials. The invention has utility in the production and optimization of the properties of high performance materials.
2. Prior Art
At present, when manufacturing multi-phase composites, the multi-phase composite microstructure usually cannot be predicted, and thus cannot be controlled, on a micron scale level. This is a major cause of low reliability and high manufacturing reject rate of the final composite product. Also, since most high performance materials are opaque, quality control of the microstructure during or after manufacture by non-destructive evaluation or testing (NDE) is not possible. Quality control is critical, often meaning the difference between life and death for persons relying on the material used in armor.
In the Rule of Mixtures for composites, the bulk properties of a composite usually are governed by the continuous phase which is not necessarily present in the greatest volume or weight. Typically, high performance monolithic ceramics are expensive to process because of the extreme processing conditions required due to their intrinsic properties such as high melting points and hardness. As a result, many high performance monolithic materials are expensive to manufacture.
To the best of the inventor""s knowledge, no one before the inventor had been able to define the criteria for an armor material to resist penetration. To date, there has been no specific correlation made between hardness, elastic modulus, toughness, strength and a material""s resistance to penetration. Now, by learning to control the microstructural bias of a multi-phase composite, a direct correlation has been made between the microstructural bias and resistance to penetration.
The inventor discloses and claims such a process for controlling the microstructural bias of multi-phase composites wherein the mixture is hot pressed at approximately 500 psi to the optimal Climbing Temperature Program temperature in co-pending U.S. patent application Ser. No. 09/071,150, which patent application is herein fully incorporated by reference.
It is to the provision to another process for controlling the microstructural bias of multi-phase composites that the present invention is primarily directed.
Briefly described, in a preferred form, the present invention is a process to control and thus predict the microstructural bias of multi-phase composites to obtain preferential positioning of the component compounds in their morphology and position in the resulting microstructure. In general, the process will cause one component phase either to locate at the grain boundaries of the second component phase (1@2) or to be homogeneously distributed in the second component phase (1in2). In a titanium diboride and alumina mixture, the process can be used to cause titanium diboride grains either to locate at the alumina grain boundaries (T@A), or to be homogeneously distributed in the alumina (TinA), using both conventional manually mixed (MM) and advanced self-propagating high-temperature synthesis (SHS) processing technologies.
A process whereby the lower cost composite material, such as titanium diboride/alumina, performs comparably to the more expensive monolithic material, such as pure titanium diboride, by causing the grains of one phase to preferentially locate at the grain boundaries of, or to be homogeneously distributed within, the other phase during densification/fusing.
A process to optimize the performance properties of multi-phase composites by preferentially biasing the microstructure to cause the phase which intrinsically has the preferred properties to influence and enhance the desired properties of the bulk composite material.
These and other objects, features, and advantages of the present invention will become more apparent upon reading the following specification in conjunction with the accompanying drawing figures.